(function flexible(window,document){
    var docEl = document.documentElement;
    var dpr = window.devicePixelRatio || 1;

    function setBodyFontSize(){
        if(document.body){
            // body默认字体大小为16px
            document.body.style.fontSize = 16 * dpr + 'px';
        } else {
            document.addEventListener('DOMContentLoaded',setBodyFontSize)
        }
    }
    setBodyFontSize();


    //这里默认平分成 10 等分（适用移动端）
    //set 1rem = viewWidth / 24;(使用PC端)
    function setRemUnit(){
        var rem = docEl.clientWidth / 120;     //1920 / 120 = 16
        docEl.style.fontSize = rem+'px';
    }

    setRemUnit()

    window.addEventListener('resize',setRemUnit);
    window.addEventListener('pageshow',function (e) {
        if(e.persisted) setRemUnit();
    });

    if(dpr >= 2){
        var fakeBody = document.createElement('body');
        var testElement = document.createElement('div');
        testElement.style.border = '.5px solid transparent';
        fakeBody.appendChild(testElement);
        docEl.appendChild(fakeBody);
        if(testElement.offsetHeight === 1){
            docEl.classList.add('hairlines');
        }
        docEl.removeChild(fakeBody)
    }

})(window,document)